Method and arrangement for controlling fuel delivery in a charge forming apparatus

ABSTRACT

The disclosure embraces a method of and an arrangement for reducing or substantially restricting delivery of fuel into the induction system or fuel and air mixing passage of a carburetor or charge forming apparatus upon rebound or reversal of direction of flow of the mixture momentarily occurring at the periods of the closing of the mixture inlet port or ports of an internal combustion engine by reducing mixture rebound velocity and increasing the pressure adjacent the zone of delivery of fuel into the mixing passage thereby preventing appreciable enrichment of the fuel and air mixture during said rebound periods.

United States Patent Holland June 12, 1973 METHOD AND ARRANGEMENT FOR CONTROLLING FUEL DELIVERY IN A CHARGE FORMING APPARATUS [21] Appl. No.: 135,145

[56] References Cited UNITED STATES PATENTS 6/1932 Malin 261/78 R 2/1933 Viel 261/DIG. 68 261/66 R 2,087,293 7/1937 Olson 2,102,113 12/1937 Djordsevitch 261/78 R 2,255,296 9/1941 Moseley 261/78 R 3,768,599 2/1965 Marsee et a1. 261/78 R 3,281,128 10/1966 Phillips IBM/DIG. 0S

FOREIGN PATENTS OR APPLICATIONS 634,624 l/1962 Canada 261/78 R 792,136 10/1935 France 261/66 R 316,664 10/1956 Switzerland 261/78 R Primary Examiner-Wendell E. Burns Attorneyl-larry O. Ernsberger [57] ABSTRACT The disclosure embraces a method of and an arrangement for reducing or substantially restricting delivery of fuel into the induction system or fuel and air mixing passage of a carburetor or charge forming apparatus upon rebound or reversal of direction of flow of the mixture momentarily occurring at the periods of the closing of the mixture inlet port or ports of an internal combustion engine by reducing mixture rebound velocity and increasing the pressure adjacent the zone of delivery of fuel into the mixing passage thereby preventing appreciable enrichment of the fuel and air mixture during said rebound periods.

38 Claims, 43 Drawing Figures PAIENYED 3.738.336

SNEUIUF'I Ill .IHI

I NVENTOR. Woe/mm i HOLLAND Mg 3W PAIEQ Jmu 2:973

17 1 Fig.1

INVENTOR. M/WAW r Ham/w PAIENIEU m1 2 2a SHEET R (If I W2 W @at I NVE NTOR.

NORMA/V F Ham/v0 47 ram/5y METHOD AND ARRANGEMENT FOR CONTROLLING FUEL DELIVERY IN A CHARGE FORMING APPARATUS The method and apparatus of the invention have particular utility with two cycle engines of the three port type because of the severity of reverse mixture flow or rebound in the mixing passage upon closing of a mixture inlet port of the engine by the engine piston. The method and apparatus of the invention have utility with both four cycle and two cycle engines which, in operation, develop reverse flow or rebound action of the fuel and air mixture upon closing of the mixture inlet port or ports of the engine by valve means such as conventional reed valves of types of two cycle reciprocating piston engines other than the three port type and with reciprocating piston engines of the four cycle type where there occurs a substantial reverse flow or rebound velocity of fuel mixture in the intake manifold transmitted to the mixing passage of the carburetor or charge forming apparatus used with the engine.

The invention relates to charge forming apparatus or carburetor and more particularly to a charge forming apparatus or carburetor for use with internal combustion engines of one or more cylinders where a single carburetor or charge forming apparatus supplies com-.

bustible fuel and air mixture for the cylinder or cylinders, the charge forming apparatus or carburetor being usable with both two cycle and four cycle engines. The invention may be embodied in carburetors of the socalled aspirated diaphragm type or of the float bowl type wherein fuel level in a chamber is controlled by a float operated valve.

The charge forming apparatus or carburetor of the invention has particular utility with engines of the two cycle type usually referred to as a three port engine, that is, a two cycle engine wherein the combustible fuel andair mixture from a carburetor is delivered into the crankcase through a port in the cylinder wall which is opened and closed by the skirt of the piston, the mixture compressed in the crankcase and delivered through a channel and mixture inlet port into the combustion chamber of the cylinder and wherein the exhaust is delivered through an exit port uncovered or opened by the piston as the piston approaches the a lower end of a power stroke. Engines of this character are particularly usable for powering snowmobiles, the engine having one or more cylinders of the three port type and of a size or capacity of ten to fifty or more horsepower.

in the operation of engines of this general character under open throttle or partially open throttle conditions, the volume and velocity of air moving through the carburetor mixing passage aspirates fuel from a fuel delivery nozzle into the air stream to provide the combustible mixture for the engine. The air flow in the mixing passage is at substantial velocity due to the suction or reduced pressure in the crankcase of the two cycle engine developed during the upward stroke of the piston. When the piston moves downward on a power stroke of a three port engine, the piston skirt closes the mixture inlet port of the manifold or mixing passage of the carburetor.

The stream of air and fuel mixture, moving at high velocity in the mixing passage or intake manifold, is impeded by the positive closing of the port by the piston skirt. This condition causes or sets up a reaction pressure or rebound of the stream of combustible mixture, resulting in stream flow in a reverse direction in the mixing passage of the carburetor toward the air inlet region of the mixing passage. The reaction or rebound velocity of the air and fuel mixture causes more fuel to be aspirated or delivered from the fuel nozzle into the reversely moving mixture stream. This results in an enrichened fuel and air mixture delivered to the engine upon the opening of the inlet port by upward movement of the piston skirt. This action is referred to as double metering or a double delivery condition.

The overrich mixture resulting by reason of the fuel added to the mixture during the reverse flow of the mixture stream under the rebound pressure condition is aggravated in carburetors embodying a supplemental or small Venturi disposed within the main Venturi, the function of the small Venturi being to enhance or increase the effectiveness of the aspiration of fuel into the mixing passage. The excess fuel in the fuel and air mixture caused by the reverse flow or rebound condition substantially impairs combustion and reduces the power output of the engine particularly at intermediate and high speeds.

The invention embraces a method of controlling fuel delivery from an orifice under the influence of engine aspiration into an air stream in a mixing passage of a carburetor or charge forming apparatus wherein aspiration set up by the velocity of the reverse flow of fuel and air mixture in the mixing passage due to rebound action or reverse flow of the mixture stream occurring upon closing of the mixture inlet port to the engine is substantially reduced at the region of delivery of fuel to thereby reduce or substantially restrict delivery of fuel and prevent appreciable enrichment of the mixture stream during the periods of reverse flow of the fuel and air mixture in the mixing passage.

An object of the invention is the provision of a method or system for controlling a fuel and air mixture in a mixing passage upon rebound or reversal of direction of flow of the mixture momentarily occurring at periods of closing of the mixture inlet port to the engine by increasing the pressure at a localized region adjacent the fuel delivery orifice to momentarily reduce aspiration of fuel into the mixing passage during rebound periods and thereby substantially avoid enrichment of the fuel and air. mixture.

An object of the invention embraces the provision of a carburetor or charge forming apparatus for use with a two cycle internal combustion engine wherein the fuel and air mixing passage of the carburetor or charge forming apparatus is equipped with a barrier or impediment disposed in the mixing passage at the upstream side of a fuel delivery orifice wherein the barrier or impediment is of a configuration providing a zone or chamber at the region of the main fuel delivery orifice in which pressure is increased upon reverse flow of fuel and air mixture occurring during periods of closing of the fuel inlet port of an engine to impair or reduce aspiration of fuel into the mixing passage at such periods.

Another object of the invention is the provision of a carburetor or charge forming device for use with an internal combustion engine of the reciprocating piston type, the carburetor or charge forming apparatus having a mixing passage and a fuel delivery orifice and including a barrier or impediment at the air inlet side of the fuel delivery orifice shaped to effect an increase in pressure at the region of delivery of fuel upon reversal of flow or rebound of the fuel and air mixture in the mixing passage occurring by reason of the closing of the mixture inlet port of the engine to prevent delivery of excess fuel into the mixing passage, the barrier or impediment having vent or passage means to control or regulate the amount of increase in pressure at the zone of delivery of fuel into the mixing passage.

Another object of the invention is the provision of a carburetor or charge forming apparatus for an internal combustion engine of the reciprocating piston type wherein the charge forming apparatus or carburetor is fashioned with a fuel and air mixing passage and orifice means for delivering fuel into the mixing passage by engine aspiration, the arrangement including a chamber in the mixing passage having an open area downstream of the mixing passage for normal fuel delivery to the engine, the chamber being configurated to establish increased pressure during periods of rebound or reversal of flow of the mixture due to closing of the mixture inlet port to the engine whereby aspiration of fuel is momentarily reduced at each period of increase in pressure in the chamber to substantially reduce the delivery of fuel into the mixing passage during the periods of rebound or reversal of directionof flow of the mixture in the mixing passage.

Another object of the invention is the provision of a carburetor having a fuel and air mixing passage for supplying mixture to an internal combustion engine, the carburetor having wall means disposed in the mixing passage adjacent the zone of delivery of fuel into the mixing passage providing a region or chamber forestablishing increased pressure upon rebound or reversal of flow of fuel and air mixture during the periods of closing of the mixture inlet port to the engine to restrict or substantially reduce aspiration of fuel during rebound periods, the chamber being fashioned with an open area or areas for controlling the extent or amount of increase in pressure so as not to impair the normal delivery of fuel and air mixture to the engine.

Another object of the invention is the provision in the mixing passage of a carburetor of the aspirated diaphragm type or of the float controlled bowl type of means for restricting delivery of fuel into the mixing passage during periods of reverse flow of the mixture or rebound action in the mixing passage resulting from closing of the mixture inlet port of the engine with l which the carburetor is used to avoid an excess of fuel in the normal fuel and air mixture in the mixing passage.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIG. 1 is a semischematic sectional view of a two cycle reciprocating piston engine of the three port type with a carburetor embodying the invention associated therewith, the carburetor being shown in side elevation;

FIG. 2 is a top planview of the carburetor shown in FIG. 1;

FIG. 3 is a view of the air inlet endof the carburetor;

FIG. 4 is a longitudinal sectional view through the carburetor, the section being taken substantially on the line 4-4 of FIG. 2;

FIG. 5 is a transverse sectional view taken substantially on the line 5-5 of FIG. 4;

. FIG. 6 is a bottom plan view of the carburetor, the diaphragm and cover plate being removed;

FIG. 7 is a fragmentary sectional view taken substantially on the line 77 of FIG. 2;

FIG. 8 is a fragmentary sectional view taken substantially on the line 8-8 of FIG. 2;

FIG. .9 is an enlarged sectional view of a fitting providing a main fuel delivery means;

FIG. 10 is a top plan view of the fitting shown in FIG. 9;

FIG. 11 is a fragmentary sectional view illustrating a modification of the pressure rebound control arrangement of FIG. 4;

FIG. 12 is a sectional view taken substantially on the line 12-12 of FIG. 11;

FIG. 13 is a view similar to FIG. 1] illustrating another modification of the pressure rebound control construction;

FIG. 14 is a sectional view taken substantially on the line 14-14 of FIG. 13;

FIG. 15 is a view similar to FIG. 11 illustrating a modification of the rebound pressure control construction;

FIG. 16 is a sectional view taken substantially on the line 16-16 of FIG. 15;

FIG. 17 is a fragmentary sectional view similar to FIG. 16 illustrating a modified arrangement of pressure relief areas of the rebound control chamber;

FIG. 18 is a longitudinal sectional view similar to FIG. 5 showing a modification of the pressure rebound control chamber construction;

FIG. 19 is a sectional view taken substantially on the line 19-19 of FIG. 18;

FIG. 20 is a longitudinal sectional view similar to FIG. 18 showing a modification of the pressure rebound control chamber;

FIG. 21 is a sectional view taken substantially on the line 21-21 of FIG. 20;

FIG. 22 is a longitudinal sectional view similar to FIG. 20 illustrating another form of pressure rebound control arrangement;

FIG. 23 is a sectional view taken substantially on the line 23-23 of FIG. 22;

FIG. 24 is a longitudinal sectional view showing another modification of pressure rebound control chamber embodying a pressure relief or vent area;

FIG. 25 is a sectional view taken substantially on the line 25-25 of FIG. 24;

FIG. 26 is a longitudinal sectional view similar to FIG. 24 illustrating a modified pattern of rebound pressure control area;

FIG. 27 is a sectional view taken substantially on the line 27-27 of FIG. 26;

FIG. 28 is a longitudinal sectional view similar to FIG. 26 illustrating another form of rebound pressure control area;

FIG. 29 is a sectional view taken substantially on the line 29-29 of FIG. 28;

FIG. 30 is a longitudinal sectional view similar to FIG. 28 illustrating a rebound pressure vent area in a wall of the rebound pressure control chamber;

FIG. 31 is a sectional view taken substantially on the line 31-31 of FIG. 30;

FIG. 32 is a longitudinal sectional view of the mixing passage of a carburetor embodying a supplemental Venturi and a rebound pressure control arrangement;

FIG. 33 is a sectional view taken substantially on the line 3333 of FIG. 32;

FIG. 34 is a longitudinal sectional view similar to FIG. 32 illustrating a modified arrangement of supplemental Venturi and rebound pressure control;

FIG. 35 is a sectional view taken substantially on the line 35--35 of FIG. 34;

FIG. 36 is an enlarged sectional view of the supplemental Venturi and rebound pressure control shown in FIG. 34;

FIG. 37 is a longitudinal sectional view of a mixing passage illustrating another form of pressure rebound control;

FIG. 38 is a sectional view taken substantially on the line 38-38 of FIG. 37;

FIG. 39 is an enlarged sectional view of the rebound pressure control arrangement shown in FIG. 37;

FIG. 40 is a longitudinal sectional view through a mixing passage and fuel bowl construction of a float type carburetor embodying a form of rebound pressure control;

FIG. 41 is a transverse sectional view taken substantially on the line 41-41 of FIG. 40;

FIG. 42 is a view of the mixture outlet end of the carburetor shown in FIG. 40, and

FIG. 43 is a view of the air inlet end of the carburetor shown in FIG. 40.

In the operation of carburetors, particularly those for delivering a fuel and air mixture to the crankcase of a two cycle engine, the more severe conditions of rebound or reverse flow of combustible mixture in the mixing passage upon closing of the inlet port to the crankcase occur particularly with engines of the three port type, the rebound action or reverse flow of the mixture usually being greatest at intermediate engine speeds under load in a range usually from 1800 to 3000 or more revolutions per minute.

The engine speed range at which substantial velocity of the reverse flow or rebound of the mixture occurs is dependent in a measure upon the type and power rating and other characteristics of a particular engine. As mixture rebound or reverse flow of mixture in the induction system or mixing passage of the carburetor is more prevalent with carburetors used with three port engines, a carburetor embodying the invention has been illustrated in association with a three port, two cycle engine. It is to be understood however, that the rebound pressure control arrangement may be embodied in carburetors used with other types of two cycle engine or with the induction system of a four cycle engine.

Referring to the drawings, and initially to FIG. 1, there is illustrated in semischematic form a two cycle engine of the three port type in association with a carburetor or charge forming apparatus of the diaphragm type embodying a form of the invention and adapted to supply a combustible mixture of fuel and air to the engine, the carburetor being further illustrated in FIGS. 2 through 8. The two cycle engine illustrated is of the single cylinder type but it is to be understood that carburetors embodying the rebound pressure control may be used with four cycle reciprocating piston internal combustion engines or with two cycle engines having two or more cylinders by providing suitable manifold means for conveying combustible mixture to each of the crankcase compartments of a multicylinder two cycle engine, or a separate carburetor embodying the rebound pressure control may be provided for each of the engine crankcase compartments.

The engine 10 is of the air cooled type and includes a cylinder 12 fashioned with a head 14, the cylinder and head being provided with cooling fins 16. The engine has a crankcase 18 providing a crankcase chamber 19. The cylinder 12 and the crankcase 18 are provided respectively with mating flanges 20 and 21 which are secured together by bolts (not shown), a conventional sealing gasket 23 being disposed between the mating flanges.

The cylinder construction and the crankcase construction are preferably fashioned of comparatively lightweight metal such as aluminum or an alloy of aluminum, the cylinder 12 having an interior sleeve or liner 25 of steel or other wear-resistant metal. The interior of the cylinder head portion 14 is shaped to provide a combustion chamber 26 and the upper wall of the cylinder head is fashioned with a threaded opening accommodating a conventional spark plug 27. Reciprocably disposed within the cylinder liner 25 is a piston 28 having a skirt portion 29 slidably fitting the interior wall of the cylindrical sleeve 25.

Journally mounted in bearings in the crankcase construction 18 is a conventional crank 30 equipped with a crank arm having a crank pin 32. The piston 28 is provided with a wrist pin 34, the wrist pin and the crank pin 32 being connected with a conventional connecting rod 35. The crankshaft is fashioned with a conventional counterweight 36. The engine illustrated is of the socalled three port type, the cylinder wall and the sleeve having a mixture inlet port 38, the port 38 mating with a passage 39 in a manifold member 40 preferably of heat insulating material.

A carburetor 42 of the aspirated diaphragm type embodying the invention has a mounting flange 44 secured to the manifold member 40 by conventional bolts 46, oneof which is shown in FIG. 1, the bolts extending through mating openings in the mounting flange and member 40 into threaded openings formed in boss portions (not shown) provided on the cylinder wall. The cylinder wall 12 is fashioned with a passage or channel 48, its upper end being in communication with a port or opening 49 in the sleeve 25, the lower end of the channel opening into the crankcase chamber 19.

The passage or channel 48 conveys fuel and air mixture from the crankcase chamber 19 into the cylinder above the head of the piston 28. An exhaust port 51 is provided in the cylinder wall and sleeve 25 through which spent gases of combustion are exhausted from the cylinder at the completion of each power stroke of the piston 28. The carburetor construction 42, which will be hereinafter described in detail, is adapted to provide a fuel and air mixture for delivery to the engine crankcase chamber 19 during each revolution of the engine.

The operation of the two cycle engine, shown in FIG. 1, is as follows: A fuel and air mixture formed in the mixing passage of the carburetor is supplied to the engine crankcase chamber 19 through the inlet port 38 in the cylinder wall and sleeve when the piston is in an uppermost position uncovering the port 38. As the piston 28 moves upwardly on a compression stroke, the port 49 and the exhaust port 51 are closed by the piston and the fuel and air mixture compressed in the combustion chamber 26.

The piston 28, moving upwardly, establishes reduced pressure or suction in the crankcase chamber 19, and when the lower edge of the upwardly moving piston skirt 29 uncovers the fuel and air mixture inlet port 38, the reduced pressure or suction in the crankcase chamber 19 is effective to aspirate combustible mixture from the mixing passage in the carburetor through the inlet port 38 into the crankcase chamber 19.

When the piston 28 is approximately at its uppermost position, a spark plug 27 ignites the mixture compressed in the combustion chamber 26 forcing the piston 28 downwardly. As the piston moves downwardly on a power stroke, the piston skirt closes the inlet port 38, the piston compressing the fuel and air mixture which has been aspirated into the crankcase chamber 19 from the carburetor. As the piston approaches its lowermost position of a power stroke, the exhaust port 51 is uncovered and the spent gases exhausted through the port 51.

After the exhaust port 51 is uncovered, the port 49 is uncovered, and the precompressed fuel and air mixture in the crankcase chamber 19 flows through the channel or passage 48 and port 49 into the chamber or space in the cylinder above the piston. For purposes of illustration, as shown in FIG. 1, the exhaust port 51 is disposed about ninety degrees from the port 49, but in the construction of an engine of this type the exhaust port 51 is usually disposed substantially diametrically opposite to the port 49 so that the mixture flowing into the cylinder through the port 49 assists in scavenging exhaust gases from the cylinder through the exhaust port 51. The above described cycle of operation occurs during each complete revolution of the engine crankshaft 30.

The carburetor 42 embodying a form of the invention is illustrated in FIGS. 1 through 8. The carburetor construction 42 is of the diaphragm type and includes a body fashioned with a fuel and air mixing passage 62 of circular cross section as shown in FIG. 4, the mixing passage including a Venturi 64 having a restricted region or choke band 65, an air inlet region 67 and a mixture outlet region 68. As shown in FIG. 1, a gasket 70 is interposed between the manifold member 40 and the mounting flange 44. The manifold member 40 is preferably of heat insulating material to retard transfer of heat from the cylinder wall to the carburetor body.

As shown in FIG. 1, the air inlet end of the carburetor body 60 is preferably equipped with an air filter construction 72 of conventional construction, the housing of the air filter being secured to the carburetor body 60 by screws 74 extending into threaded openings 75 provided in the carburetor body. Disposed in the air inlet region-67 of the mixing passage is a choke valve 77 mounted upon a shaft 78, the shaft being joumaled in diametrically arranged bores provided in the carburetor body. An end of the shaft 78 exterior of the body is equippedwith an arm 79 for manipulating the choke valve 77 for engine starting purposes.

Disposed in the region 68 of the mixing passage 62 is a disc-type throttle valve 80 secured on a throttle operating shaft 81 by a screw 82. Mounted on the throttle shaft 81 exteriorly of the body 60 is an arm 84 for manipulating the throttle valve 80. A coil spring 86 surrounds the shaft 81 adjacent the arm 84, one end of the spring being connected with the arm 84, the ther end engaging an abutment on the carburetor body. The spring 86 biases the throttle valve 80 toward near closed or idling position, the throttle valve being shown in idling position in FIG. 4.

The body 60 is fashioned with a projection or lug 88 having a threaded bore accommodating an adjusting screw 90, an end region of the screw 90 being tapered as at 91 for cooperation with a portion or extension 92 on the manipulating arm .84 for effecting an engine idling adjustment position of the throttle valve 80. A coil spring 93 surrounds the engine idling adjusting screw 90 between the head of the screw and the lug 88 providing friction for retaining the screw in adjusted position.

The carburetor body 60 is formed with a comparatively shallow recess providing a fuel chamber 95 of generally circular configuration, and a flexible membrane or diaphragm 97 extends across the recess providing a flexible wall of the fuel chamber 95. An annular gasket 98 is disposed between the peripheral region of the diaphragm 97 and the carburetor body 60. A substantially circular member 100 is disposed beneath the diaphragm 97 and is fashioned with a central circular recess 102 providing a space to accommodate flexing movements of the diaphragm 97. The space or recess 102 is vented to the atmosphere by a vent passage 103, shown in FIG. 4.

Associated with the carburetor illustrated in FIGS. 1 through 8, is a diaphragm-type fuel pump construction 105 secured to the carburetor body 60. The fuel pump construction 105 is conventional, such as the pulse operated diaphragm fuel pump illustrated in Phillips US.

Pat. No. 2,796,838. Disposed beneath the member 100 is a member 107, a pumping diaphragm 108 being disposed between the members 100 and 107. The pumping diaphragm 108 is vibrated by varying pressure pulses set up during engine operation in the engine crankcase chamber 19. The member 100 is fashioned with a cavity forming the pumping or pulse chamber 110 at one side of the diaphragm 108, and the member 107 is fashioned with a recess providing a fuel chamber 112.

The pulse or pumping chamber 110 is in communication with a fitting or nipple 114, shown 'in FIG. 2, and the nipple 114 is in communication with the engine crankcase chamber 19 by a tube or connection 116, shown in FIG. 1. The pumping diaphragm 108 is fashioned with flap valves, one of which is illustrated at 118 in FIG. 5, to effectpumping of liquid fuel from a supply through the fuel chamber 112 of the pump thence into registering passages 119 and 120 in member 100 and the carburetor body 60, the passage 120 being in communication with a fuel inlet duct or passage 122.

The members 100 and 107, the pumping diaphragm 108, the fuel metering diaphragm 97 and gasket 98 are held in assembled relation by screws 124 extending into threaded bores 125 in the body 60. A fitting 126 is secured to member 107 by a screw 127, as shown in FIG. 5, the fitting 126 having a nipple 128, shown in FIG. 1, which is connected with a fuel supply tank by means of a flexible tube (not shown) in a conventional manner. Disposed between the fitting 126 and member 107 is a fuel strainer or screen 130, shown in FIG. 5, for filtering the incoming liquid fuel before it flows into the chamber 112 through channel means (not shown).

The varying fluid or gas pressures developed in the engine crankcase by the two cycle engine are communicated through the tube 116, shown in FIG. 1, nipple 114 and a channel (not shown) in the member 100 to the pumping chamber 110 to flex or vibrate the pumping diaphragm 108 and thereby effect a pumping action in the fuel chamber 112 to pump fuel from a supply through the screen or filter 130 and through the fuel chamber 112 to the fuel passages 119, 120 and 122.

Disposed within a recess 132 forming a part of the fuel chamber 95 is a lever 134 fulcrumed or pivoted intermediate its ends upon a fulcrum pin 135 carried by the body 60. Positioned close to the fulcrum pin is an expansive coil spring 136 normally biasing the lever 134 in a clockwise direction, as viewed in FIG. 5, about the fulcrum pin 135. The distal end of the long arm of the lever is arranged to be engaged by a head 137 of a rivet mounted at the central region of the diaphragm.

Reinforcing discs 138 and 139 are disposed at oppo site sides of the diaphragm 97, the shank of the rivet extending through registering openings in the discs and the diaphragm, the lower end of the rivet being swaged to secure these components in assembled relation as shown in FIG. 5. The short arm 141 of the lever is arranged for engagement with an end of a fuel inlet valve body 143. The carburetor body 60 has a threaded bore 145 accommodating a threaded fitting or valve guide means 146 having a bore in which the valve body 143 is disposed for slidable movement.

The valve body 143 is of polygonal cross section to facilitate flow of liquid fuel past the valve body into the fuel chamber 95. The valve body or member 143 is fashioned with a cone-shaped valve portion 147 which cooperates with an inlet port 148 provided by an annular valve seat 149. The fuel inlet port 148 is in commu nication with the interconnecting passages or channels 119, 120 and 122 which receive fuel under comparatively low pressure from the fuel chamber 112 of the fuel pump 105.

The form of carburetor or charge forming device illustrated in FIGS. 1 through 8 is fashioned with fuel channel systems and orifice means for delivering liquid fuel into the mixing passage 62 under the influence of engine aspiration or reduced pressure in the mixing passage for normal and high speed engine operation and for engine idling. The carburetor body is fashioned with a main or primary fuel delivery system which includes a main fuel delivery orifice 150, the main fuel delivery arrangement being hereinafter described.

The carburetor body is fashioned with a secondary fuel delivery system which includes an engine idling orifice 152 and a low speed orifice 153, shown in FIGS. 4 and 6. The engine idling orifice 152 is at the downstream or left-hand side of the throttle valve 80 as viewed in FIG. 4. The secondary fuel delivery system is inclusive of a small supplemental chamber 155, the lower end of which is closed by a Welch plug 156. As shown in FIG. 8, the carburetor body is fashioned with a passage or bore 158 which receives fuel from the fuel chamber 95 through a passage or channel 96. The bore 158 is in communication with the chamber 155 by a restricted passage 160.

A portion of the bore 158 is threaded to accommo' date the threaded portion 162 of a valve body 163, the valve body 163 having a needle valve portion 164 cooperatingwith the restricted passage 160. The valve body 163 is provided with a knurled head 166 for manipulating the valve body 163 and needle portion 164 for regulating flow of fuel from the fuel chamber 95 into the small chamber for delivery through the engine idling orifice 152 and the low speed orifice 153. A coil spring 167 is disposed between a sealing gasket 168 and the knurled head 166 to exert pressure on the sealing gasket and establish friction for maintaining the valve body 163 in adjusted position.

The channel system for delivering fuel from the fuel chamber 95 through the main orifice into the mixing passage is illustrated in FIGS. 4 and 7 and is inclusive of a bore 170 which accommodates a member or fitting 172, the lower end of the bore adjacent the fuel chamber 95 being closed by a Welch plug 174. The fitting 172 is illustrated on an enlarged scale in FIGS. 9 and 10. The fitting 172 is provided with a peripheral flange 176 engaging a ledge provided by a threaded counterbore 178. The upper exterior region of the fitting 172 is threaded into the threaded counterbore 178.

The fitting 172 is fashioned with a central passage 179 in communication with a counterbore 180 in which is disposed a ball check valve 182 which is prevented from dislodgement from the counterbore by a grid 183. The ball valve 182 is adapted to seat against a frustoconical surface 184 but is loosely disposed in the counterbore in the fitting so that fuel may flow past the ball and out of the main orifice 150.

Referring to FIG. 7, the carburetor body 60 is fashioned with a bore 185 which is in communication with the fuel chamber 95 by a channel or passage 187 and with the well or chamber provided by the bore 170 by a restricted passage 188. A portion of the bore 185 is threaded to accommodate a threaded portion 191 of the valve body 190, the valve body having a needle valve portion 192 cooperating with the restricted passage 188.

The valve body is provided with a head 194 for manipulating the needle valve 192 to regulate flow of fuel from the fuel chamber 95 through the restricted passage 188 into the well 170 for delivery through the passage 180 in the fitting 172 thence through the main orifice 150 into the mixing passage for normal and high speed engine operation. The check ball or valve member 182, being loosely disposed in the counterbore 180 of the fitting 172, is for the purpose of preventing back bleeding of air from the mixing passage into the fuel channel system when fuel for engine idling purposes is being delivered through the secondary orifice 152.

During normal operation of the two cycle engine with which the carburetor is used, the throttle valve 80 being in partial or full open position when the mixture inlet port 38, shown in FIG. 1, is uncovered or opened upon upward movement of the piston skirt 29, the aspiration or reduced pressure in the engine crankcase 19 is effective in the mixing passage 62 of the carburetor to aspirate or efiect the delivery of fuel through the main orifice 150 into the high velocity air stream moving through the mixing passage. The fuel delivered through the main orifice 150 flows from the fuel chamber 95 through the communicating passages 187, 185

and 188 and through the well 170 and past the check ball 182. I

The aspiration or reduced pressure in the mixing passage 62 is transmitted through these' communicating passageways or channels to the fuel chamber 95 and is effective to elevate or flex the diaphragm 97, shown in FIG. 5, swinging the lever 134 about its fulcrum 135 in a counterclockwise direction whereby the valve body 143 moves downwardly and fuel from the passage 122,

under low pressure from the fuel pump 105, flows past the inlet needle valve portion 147 and into the fuel chamber 95 to replenish the fuel delivered into the mixing passage.

When the throttle valve 80 is moved to near closed or engine idling position, as shown in FIG. .5, fuel from the chamber 95 is aspirated into the mixing passage through the engine idling orifice 152 at the downstream side of the throttle valve, the fuel for engine idling operation flowing from chamber 95 through passage 96, bore 158, past the needle valve portion 164 and through the restricted passage 160 and the supplemental chamber 155, shown in FIG. 8. When the throttle is partially opened, fuel is additionally aspirated from the chamber 155 into the mixing passage through the orifice 153 for low speed engine operation.

During operation of the engine, when the mixture inlet port 38 is opened upon upward movement of the piston skirt 29, the suction or reduced pressure in the crankcase 19 effects air flow through the mixing passage. With the throttle valve 80 in near closed or engine idling position, fuel is delivered through the orifice 152 into the mixing passage for engine idling. When the throttle valve is opened slightly, fuel is delivered through the orifice 153 for low speed engine operation. With increased opening of the throttle valve, air flow and air velocities in the mixing passage are increased and fuel is aspirated from the main orifice 150 into the high velocity air stream, providing a combustible mixture for normal and high speed engine operation.

At engine idling and low speed engine operation, the obturation or closing of the mixture inlet port 38 momentarily reduces mixture flow in the mixing passage and passage 39 tending to cause a rebound or reverse flow of the mixture in the mixing passage. However, at engine idling and low engine speeds, the velocity of the reverse flow of the mixture is comparatively low and does not appreciably impair or modify delivery of fuel into the mixing passage.

At normal or higher speeds of engine operation, the velocity of the air stream moving through the mixing passage is greatly increased, and during periods of closing of the fuel inlet port 38, the high velocity stream of combustible mixture is impinged against the piston skirt 29 closing the port 38 causing an abrupt reversal of flow or rebound of the fuel and air mixture in the mixing passage toward the air inlet.

Such rebound or reverse flow of air and fuel mixture is of substantial velocity and continues to maintain a low pressure and hence aspirating effect on the main orifice or fuel delivery nozzle 150 so that fuel continues to be delivered into the normal fuel and air mixture while moving in the reverse direction resulting in an excess amount of fuel in the mixture delivered to the engine upon opening of the mixture inlet port 38. This overrich fuel and air mixture reduces the power of the engine because of improper combustion of the mixture. This condition is usually referred to as double meterm fivhile rebound or reverse flow of mixture occurs to a limited extent in carburetors used with most engines, the condition is particularly severe in three port two cycle engines where the manifold or passage 39 is very short and the mixure column likewise comparatively short. In two cycle engines of the type wherein a oneway reed type valve is utilized at the inlet port between an engine crankcase and the mixing passage ofa carburetor, the reed valve isflexible and does not effect a severe abrupt impediment and rebound of mixture flow as in a two cycle engine having a positively closing valve such as provided by the piston skirt 29 for the mixture inlet port 38 shown in FIG. 1.

Multiple cylinder engines having comparatively long intake manifolds set up only minor mixture rebound reactions because the length of the mixture column in the longer manifold provides a damping action of pressure rebound or reverse flow of mixture resulting from closing of a mixture inlet port.

The carburetor or charge forming apparatus of the present invention provides a method of and means for impeding the rebound reaction or reverse flow of the fuel and air mixture adjacent the main fuel delivery orifice to establish or build up an increase in pressure at the region of delivery of fuel and greatly reduce the velocity of the reversely flowing mixture to thereby restrict or reduce momentarily, after each closing of the mixture inlet port 38, the delivery of fuel into the reversely flowing mixture in the mixing passage and substantially prevent excess fuel being delivered into the normal fuel and air mixture formed in the mixing passage prior to rebound reaction.

One form of construction for accomplishing this purpose is illustrated in FIGS. 3, 4, 5 and 7. Disposed in the mixing passage 62 adjacent the main fuel delivery orifice is a means or member 196 which, in the embodiment illustrated in FIGS. 3, 4, 5 and 7, is integral with the carburetor body 60. In this form of the invention, the means 196 is inclusive of a wall or portion 198 at the air inlet or upstream side of the fuel delivery orifice l50.providing an impediment or barrier for restricting or controlling reverse flow of mixture adjacent the orifice 150. The member 196 is preferably fashioned with a hollow portion or sleeve 200 defining a rebound pressure and velocity control chamber 202. The wall 198 is provided with an opening or open area 204 spaced from the main orifice 150 and in communication with the upper region of the control chamber 202.

During engine operation at speeds wherein the air stream moves through the mixing passage at high velocities resulting in high velocity reverse flow or rebound action of the fuel and air mixture stream upon closing of the mixture inlet port of the engine, the wall 198 and chamber 202 cooperate to substantially reduce reverse flow or rebound of the mixture adjacent the main fuel orifice 150, the restriction or impedance of the reversely moving mixture stream substantially reduces its velocity and increases the pressure adjacent the main fuel orifice to restrict or reduce aspiration adjacent the main fuel orifice 150 and thereby momentarily reduce delivery of fuel through the main orifice into the control chamber 202.

The opening or open area 204 serves several purposes. It facilitates flow of air downstream from the air inlet into and through the control chamber 202 whereby engine aspiration during downstream flow of air in the mixing passage effects normal fuel delivery from the main orifice 150. The opening 204 admits air for mixing with or aerating the fuel in the chamber 202. The open area functions as a relief or vent upon reverse flow of the mixture into the control chamber 202 so that the pressure set up in chamber 202 during rebound does not increase to an extent as to prevent or impair normal delivery of fuel from the main orifice during open periods of the mixture inlet port 38.

It is found preferable that the reduced rebound velocity of the mixture affecting fuel delivery be controlled so that there is sufficient retained velocity of the rebound mixture at or in the control chamber providing sufflcient aspiration to effect the delivery of a small amount of fuel from the orifice during rebound in order to maintain continuity of delivery of fuel from the orifice. The amount of fuel delivered during rebound should preferably be held to a minimum so that-the mixture flow downstream following rebound periods will contain but a very small amount of additional fuel insufficient to appreciably modify the ratio of fuel to air in the normal mixture so as not to impair efficient combustion of the mixture in the engine cylinder or cylinders.

By maintaining continuity of delivery of some fuel during rebound periods of the mixture, there is a practially instantaneous recovery of normal fuel delivery under engine aspiration following rebound periods as fuel is already flowing from the fuel delivery orifice during rebound periods and normal engine aspiration simply increases the flow of fuel for engine operation.

It is to be understood that the reduced velocity of the rebound mixture and increased pressure conditions in the control chamber 202 may vary with different engines and at different rebound velocities of the mixture in the mixing passage. The size of the open area 204 and its location in the wall or barrier 198 may be varied dependent upon the pressure rebound control desired in the chamber 202 to secure effective and efficient operation of the engine by reducing or restricting fuel delivery from the'oriflce 150 during rebound periods and yet provide sufficient air flow downstream through the chamber 202 to normally aspirate fuel from the main orifice for a proper fuel and air mixture delivered into the engine crankcase at each opening of the inlet port 38 to provide a full power mixture for engine operatron. I

While in the embodiment illustrated in FIGS. 3, 4 and 5, the sleeve portion 200 of member 196 providing the control chamber 202 extends inwardly to about the mid region of the mixing passage, as shown in FIG. 4, it is to be understood that the member 196 may vary in size dependent upon thesize of the mixing passage of the carburetor, the size and characteristics of the engine with which the carburetor is used and the extent of pressure to be developed in the control chamber to reduce fuel delivery during the rebound or reverse flow of the mixture in the mixing passage.

The interior wall 206 of the control chamber 202 is of circular cross section and is preferably flared in a downstream direction and defined by a curved or toroidal surface, as illustrated in FIG. 4, to provide adequate rebound velocity and pressure control. As the cross sectional area of the control chamber is progressively reduced toward the barrier or impediment 198, the increase in pressure in the control chamber is augmented because the outlet area of the chamber is greater than the area of the chamber adjacent the wall 198.

By varying the degree of flare or the curvature of the interior wall 206, variable control of the rebound pressure developed within the chamber 202 may be attained. As shown in FIG. 4, it is preferable that the outlet end of the control chamber 202 be disposed substantially at the most restricted region or choke band- 65 of the Venturi 64 for efficient delivery of the fuel and air mixture from the control chamber 202 into the air stream moving through the Venturi.

An advantage of the curved or toroidal shaped wall 206 of the member or means 196 enables more efficient air flow downstream through the opening or open area 204 as the flared configuration of the interior surface 206 has a Venturi effect on air flow through the chamber in a downstream direction toward the mixture outlet of the carburetor, thus augmenting the normal effect of engine aspiration on the main orifice to deliver the required amount of fuel for an efficient fuel and air mixture.

The form of the invention embodied in the carburetor illustrated in FIGS. 1 through 8 has greatly improved the operation of three-port two cycle engines, particularly engines of one cylinder and two cylinder types extensively used for powering snowmobiles. In conventional carburetors, it is usually found that the fuel economy is greater from a mid range engine speed down to a low speed range. The power of engines of this character used with conventional carburetors usually increases from 4000 to 5000 revolutions per minute of the engine.

It is found that with the carburetor of the invention used with an engine of the above-mentioned character that an increase in power is attained as the speed of the engine is lowered below about 3000 revolutions per minute as compared with the power output of the engine equipped with a conventional carburetor. It is believed that the increase in power is attained because there is a greater divergence of the mixture issuing from the outlet of the control chamber 202 and that this action provides in the main mixing passage 62 a more homogeneous fuel and air mixture than is attained through the use of a normal small supplemental or secondary Venturi disposed in a main Venturi.

With the conventional small Venturi in a mixing passage adjacent a main fuel delivery orifice, it is believed that the mixture in the mixing passage tends to be more stratified, the richest mixture being delivered along the axis of a small Venturi with a minimum of divergence of the rich mixture flowing from the small Venturi into the main air stream in the mixing passage.

FIGS. 11 and 12 illustrate a modified form of means for reducing the velocity of reverse flow of mixture and pressure control at the region of a main orifice for momentarily reducing or impairing delivery of fuel into the mixing passage during rebound or reverse flow of the mixture occurring at periods of closing of the mixture inlet port to the engine. The carburetor body 60a is fashioned with a mixing passage 62a of the character illustrated in FIG. 4 including a Venturi 64a and an air inlet region 67a.

Disposed in the mixing passage is a means or member 208 which includes a barrier, wall or impediment 209 and a cylindrically-shaped sleeve portion 210, the sleeve portion having a hollow interior defining a control chamber 212, the wall region of the control chamber 212 being of partial toroidal curvature flared outwardly as at 214 toward the outlet 215 in the direction of normal flow of mixture in the mixing passage. A fitting 172a is threaded into a bore a in the body 600 and provides a main fuel delivery orifice 150a, the fitting 172a being of the same character as the fitting 172 shown in FIGS. 4, 9 and 10. The lower end of the bore 170a is closed by a Welch plug 174a.

In this form of rebound mixture velocity and pressure control arrangement, the wall 209 is provided with an opening or open area 216. The opening 216 provides for air flow from the inlet region 67a through the pressure control chamber 212 for aerating the fuel aspirated from the main orifice 150a. In this arrangement, the opening or open area 216 is disposed relatively close to the fuel delivery orifice 1500. This position of the opening 216 may be desirable with certain sizes or types of two cycle engine for efficient operation. The imperforate area of the wall 209 provides an effective barrier for reducing the velocity of the rebound mixture and increasing the pressure in the control chamber 212 to substantially reduce delivery of fuel momentarily following periods of closing of the mixture inlet port of the engine.

FIGS. 13 and 14 illustrate another modification of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice, the construction shown in these figures being similar to the construction illustrated in FIG. 1 1. The carburetor body 6017 is fashioned with a mixing passage 62b including a Venturi 64b and an air inlet re gion 67b. Disposed in the mixing passage is a means or member 218 which includes a barrier or wall portion 219 and a cylindrically-shaped sleeve portion 220, the sleeve portion having a hollow interior defining a control chamber 222.

The wall region 224 defining a portion of the chamber 222 is of partial toroidal curvature and flared outwardly toward its outlet 225 in the direction of normal downstream flow of mixture in the mixing passage. A fitting 172b is threaded into a bore l70b in the body 60b and provides a main fuel delivery orifice 150b, the fitting being of the character illustrated in FIGS. 9 and 10. The region of the bore 170b beneath the fitting 172b is closed by a Welch plug 174b. In this form the wall 219 is fashioned with an opening or open area 226, the opening being of substantially circular cross section and defined by a curved surface 227 preferably in the shape of a partial section of a torus, which configuration, being similar to the entrance region of a Venturi, facilitates smooth flow of air into the control chamber 222 for aerating the fuel delivered into the chamber.

The surface 227 may also be designated as a curved surface of revolution. The shape of the surface 227 defining the opening 226 facilitates high velocity of air movement through the control chamber 222 in a downstream direction to provide efficient aspiration for effecting delivery of fuel into the control chamber 222 and thence into the main air stream flowing through the mixing passage. The wall surface 228 provides an abrupt impediment or barrier to promote a rapid reduction in rebound velocity of mixture and an increase in pressure in the control chamber upon reverse of flow or rebound of the mixture to momentarily reduce delivery of fuel from the orifice 15% following closing periods of the mixture inlet port to the engine. The flaring surface 224, during reverse flow of the mixture, provides for convergence of reversely flowing mixture into the control chamber, this factor tending to augment the increase in pressure in the control chamber,

FIGS. 15 and 16 illustrate another modification of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The construction shown in FIGS. 15 and I6 is similar to the construction illustrated in FIG. ll.

The carburetor body c is fashioned with a mixing passage 620 which includes a Venturi 64c and an air inlet region 67c. Disposed in the mixing passage is a means or member 229, integral with the carburetor body, which includes a barrier or wall portion 230 and a cylindrically-shaped sleeve portion 231, the sleeve portion having a hollow interior defining a control chamber 232.

The wall region 233 defining a portion of the chamher 232 is of partial toroidal curvature and flared outwardly toward its outlet 234 in the direction of normal downstream flow of mixture in the mixing passage. A fitting l72c is threaded into a bore 1700 in the body 600 and provides a main fuel delivery orifice 1506, the fitting being of the character illustrated in FIGS. 9 and 10. The region of the bore 1700 beneath the fitting 172c is closed by a Welch plug 174c. In this form the wall 230 is fashioned with a plurality of spaced openings 235 providing an open area. There are four openings 235 illustrated in the wall 230 arranged in spaced relation as shown in FIG. 16. The openings 235 facilitate high velocity of air movement through the control chamber 232 in a downstream direction to aerate the fuel in the chamber 232 and as an assist in aspirating fuel into the control chamber 232 and thence into the main air stream flowing through the mixing passage. The unperforated region of the wall surface 237 provides an impediment or barrier to promote'a reduction in rebound velocity of mixture and an increase in pressure in the control chamber upon reverse of flow or rebound of the mixture to momentarily reduce delivery of fuel from the orifice 1500 following closing periods of the mixture inlet port to the engine.

FIG. 17 is a fragmentary sectional view similar to FIG. 16 illustrating a modified arrangement of openings in a wall of the control chamber of the general character shown in FIG. 15. In the arrangement shown in FIG. 17, the carburetor body 60d is fashioned with a mixing passage including a Venturi configuration 64d. Disposed in the mixing passage and integral with the body 600! is a means or member 240 of the same general configuration as the member 229 shown in FIGS. 15 and 16. The member 240 is made integral with the body 60d, the member 240 having a control chamber 242 of the character shown in FIG. 15. The member 240 is disposed in reference to the main orifice provided by the fitting 172d in the same manner as illustrated in FIG. 15.

The member 240 includes a wall 243 provided with three openings 244 disposed and spaced in the manner illustrated. The openings 244 provide for air flow from the air inlet region of the mixing passage and through the pressure control chamber 242 for normal aspiration of fuel from the main orifice and for aerating the fuel in the chamber 242. Upon reverse flow of the mixture or rebound due to closing of the mixture inlet port of the engine, the unperforated region of the wall 243 provides a barrier or impediment for reducing the velocity of the rebound mixture and increasing the pressure in the control chamber to temporarily reduce or restrict delivery of fuel by aspiration into the control chamber from the main nozzle.

The arrangement of relief openings 244 for the chamber 242 may be found desirable for use with engines in which the closing of the mixture inlet port sets up a reverse flow or rebound of mixture of high velocity in order to prevent an increase in the pressure in the control chamber 243 of such magnitude as to interrupt delivery of fuel from the fuel delivery orifice.

FIGS. 18 and 19 illustrate another modification of mixture rebound velocity and pessure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The carburetor body 60e is fashioned with a mixing passage 62e which includes a Venturi 64 and an air inlet region 67e. Disposed in the mixing passage integral with the body 60e is a means or member 248 which includes a barrier or wall portion 249 and a partial cylindrically-shaped sleeve portion 250, the sleeve portion having a hollow interior defining a control chamber 252.

A fitting 172e is threaded into a bore 170e in the body 60e and provides a main fuel delivery orifice 150e, the fitting being of the character illustrated in FIGS. 9 and 10. The region of the bore 170e beneath the fitting is closed by a Welch plug 174e. In this form the wall 249 is fashioned with an opening or open area 253 for admitting air into the chamber in a downstream direction for aerating the fuel in the chamber 252 and as an assist in the aspiration of fuel into the control chamber 252 thence into the main air stream flowing through the mixing passage.

The imperforate region of the wall 249 provides an abrupt impediment or barrier to promote a reduction in rebound velocity of mixture and an increase in pressure in the control chamber upon reverse of flow or rebound of the mixture to momentarily reduce delivery of fuel from the orifice 150e following closing periods of the mixture inlet port to the engine.

In the arrangement shown in FIGS. 18 and 19, the partial cylindrically-shaped sleeve 250 may be provided with an opening 255 in substantial alignment with or opposite the main orifice 1502. The opening 255 facilitates delivery by aspiration of some fuel from the main orifice through the opening into the air stream in the mixing passage thereby promoting a more homogeneous fuel and air mixture delivered through the outlet of the mixing passage 62d. The size or area of the openings 253 and 255 may be calibrated to secure most efficient operation of the engine with which the carburetor is used and to provide proper mixture rebound control to effectively reduce delivery of fuel following closing periods of the mixture inlet port to the engine.

FIGS. 20 and 21 illustrate another modification of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. T-he carburetor body 60f is fashioned with a mixing passage 62fwhich includes a Venturi 64f and an air inlet region 67f. Disposed in the mixing passage is a means or member 257 integral with the body 60f and of partial cylindrical shape having a hollow interior defining a control chamber 258. A fitting l72f is threaded into a bore l70fin the body 60f and provides a main fuel delivery orifice l50f, the fitting being of the character illustrated in FIGS. 9 and 10. The region of the bore 170f beneath the fitting is closed by a Welch plug 174 In this form, the end or region of the member 257 adjacent the air inlet region 67f is provided with a wall means or member 260 which may be in the form of a Welch plug, as illustrated in FIG. 20. The member 260 is provided with an opening or open area 261 to facilitate flow of air from the inlet region into the control chamber 258 for aerating the fuel aspirated from the main orifice 150 into the chamber 258. The downstream end of the member 257 is provided with a wall 267 having a plurality of openings or perforations 263 through which fuel aspirated from the main orifice f mixed with air admitted through the opening 261 is delivered downstream into the mixing passage 62fto provide a normal combustible mixture for the engine.

During periods of reverse flow or rebound of the mixture in the mixing passage 62f following periods of closing of the mixture inlet port to the engine, the portion of the reversely flowing mixture in alignment with the member 257 is impacted against the unperforated region of the wall 262 and some of the mixture flows through the openings 263 in an upstream direction into the chamber 258, reducing the velocity of the portion of the mixture adjacent the main orifice and increasing the pressure within the control chamber 258 and thereby momentarily reducing delivery of fuel through the orifice 150f.

Thus the walls 260 and 262 of member 257 provide impediments or barriers to control or increase the pressure developed in the chamber 258 upon rebound or reverse flow of the mixture so as to prevent delivery of a substantial amount of excess fuel into the mixing passage upon reversal of flow or rebound of the mixture in the mixing passage.

FIGS. 22 and 23 illustrate another modification of mixture rebound velocity and control arrangement in the region of the mixing passage adjacent the main fuel delivery orifice. The carburetor body 60g is fashioned with a mixing passage 62g which includes a Venturi 64g and an air inlet region 67g. A fitting 172g is threaded into a bore g in the body 60g and provides a main fuel delivery orifice 150g, the fitting being of the character illustrated in FIGS. 9 and 10. The region of the bore 170g beneath the fitting is closed by a Welch plug 174g.

In this form of the invention, a means or member 265 extends into the mixing passage 62g preferably at the choke band region of the Venturi 643, that is, at the region of highest velocity of air movement through the mixing passage. The member 265 has a tubular portion 267 and is fashioned at its lower end with an outwardly extending flange or ledge 269. The carburetor body 60g is fashioned with a bore snugly receiving the tubular portion 267, the bore accommodating such portion terminating in a counterbore receiving the flange or.

ledge 269.

The hollow interior or chamber 271 is in vertical alignment with the main fuel delivery orifice provided in the fitting 172g. The portion 272 of the member 265 extending into or disposed in the mixing passage 62g is of semiannular cross section providing an opening or outlet 273 downstream of the mixing passage, fuel delivered from the main orifice 150g flowing through the passage or chamber 271 into the mixing passage through the opening or outlet region 273 for normal engine operation.

The upper end of the semiannular portion 272 of member 265 terminates in a cap or cover portion 275 extending downstream of the mixing passage. The chamber controls the reverse flow of mixture or rebound adjacent the main orifice occurring during periods of closing of the mixture inlet port to the engine. The cap or cover portion 275 is preferably of semicone shape, as shown in FIG. 23, and the taper of the semicone shape being in a downstream direction toward the axis of the mixing passage.

This divergence of the portion 275 toward the axis of the mixing passage assists in dispersing the fuel aspirated through the main orifice toward the axis of the mixing passage and thereby obtain improved distribution of fuel in the air stream moving through the mixing passage 62g. The configuration of the portion 275 also enhances the effectiveness of the control chamber 271 in reducing the rebound velocity of the mixture at the region adjacent the fuel delivery orifice and momentarily increases the pressure in the chamber 271 to reduce or restrict delivery of fuel into the mixing passage during rebound or periods of mixture flow in a reverse direction.

As the portion 272 of the member 265 is of semiannular cross section, such configuration provides a wall or barrier effective in controlling mixture rebound but such configuration does not impair efficient aspiration or normal delivery of fuel into the mixing passage.

FIGS. 24 and 25 illustrate another modification of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The construction shown in these figures is similar to the construction illustrated in FIGS. 1 1 and 12. The carburetor body 60h is fashioned with a mixing passage 62h including a Venturi 64h in an air inlet region 67h. Disposed in the mixing passage is a means or member 278 which includes a barrier or wall portion 279 and a generally cylindrically-shaped sleeve portion 280, the sleeve portion having a hollow interior defining a control chamber 281.

The wall region 282 defining the chamber 281 is of partial toroidal curvature and flared outwardly toward its outlet 283 in the direction of normal flow of mixture in the mixing passage. A fitting l72h is threaded into a bore l70h in the body 60h and provides a main fuel delivery orifice 150h, the fitting being of the character illustrated in FIGS. 9 and 10. The lower end of the bore l70h is closed by a Welch plug l74h.

In this form the wall 279 is fashioned with an opening or open area 284 for admitting air into the chamber 281 in a downstream direction for aerating the fuel in the chamber 281 and as an assist in the aspiration of fuel into the control chamber 281 for delivery into the mixing passage. The position of the opening 284 in the wall 279 may be varied to attain efficient aspiration of fuel into the chamber 281.

The curvature of the wall region 282 defining the control chamber 281 provides a progressively reduced cross sectional area toward the wall or impediment 279 which augments the increase in pressure in the control chamber during mixture rebound. The outwardly flared curved surface 282 of the chamber 281 also promotes efficient air flow downstream through the opening 284 as the surface 282 has a Venturi effect on the air flow through the chamber 281.

In the arrangement shown in FIGS. 24 and 25, the partial cylindrically-shaped sleeve 280 is provided with an opening 286 in alignment with or opposite the main orifice 150k. The opening 286 facilitates aspiration of some fuel from the main orifice through the opening into the air stream in the mixing passage 62h enhancing a more homogeneous fuel and air mixture in the mixing passage. The opening 286 provides a vent to restrict and control increase of pressure in the chamber upon mixture rebound. The size of the opening 286 and its relative position in the sleeve portion 280 may be varied to attain desired mixture rebound control.

FIGS. 26 and 27 illustrated another modification of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The construction shown in these figures is similar to that illustrated in FIGS. 24 and 25. The carburetor body 60j has a mixing passage 62j including a Venturi 64j and an air inlet region 67j. Disposed in the mixing passage is a means or member 288 which includes a barrier or wall portion 289 and a generally cylindrically-shaped sleeve portion 290, the sleeve portion having a hollow interior providing a control chamber 291.

The surface 292 of the sleeve portion defining the chamber is of partial toroidal curvature and flared outwardly toward its outlet 293 in the direction of normal flow of mixture in the mixing passage. A fitting l72j is threaded into a bore 170j in the body 60] and provides a main fuel delivery orifice j. The lower end of the bore i is closed by a Welch plug 174j. The wall 289 is provided with a plurality of openings 295 providing an open area for admitting air into the chamber 291 for aerating the fuel in the chamber and augmenting the aspiration of fuel into the control chamber.

The openings 295 may be varied in size and position in the wall as may be desired to attain efficient fuel delivery from the main orifice and mixture rebound control. The unperforated region of the wall 289 provides an impediment or barrier to promote a rapid reduction in velocity of the rebound mixture and increase in pressure in the control chamber 291 to momentarily reduce delivery of fuel from the orifice l50j following closing periods of the mixture inlet port to the engine.

The sleeve portion 290 may be provided with an opening 296 preferably disposed opposite the main orifice 150j, the opening 296 enhancing aspiration of some fuel through the opening into the air stream in the mixing passage to promote a more homogeneous fuel and air mixture. The opening 296 provides a vent or relief area to control the extent of increase in pressure in the chamber 291 upon mixture rebound, and the size of the opening may be varied to attain desired rebound control.

FIGS. 28 and 29 illustrate another form of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The construction shown in FIGS. 28 and 29 is similar to the construction illustrated in FIGS. 26 and 27. The carburetor body 60k is fashioned with a mixing passage 62k which includes a Venturi 64k and an air inlet region 67k. Disposed in the mixing passage is a means or member 298 which includes a barrier or wall 299 and a cylindrically-shaped or sleeve portion 300 having a hollow interior defining a control chamber 301.

The interior surface 302 of the portion 300 defining the chamber is of toroidal curvature and flared outwardly toward the outlet 303 in the direction of normal flow of mixture in the mixing passage. A fitting 172k is threaded into a bore 170k in the body 60k and provides a main fuel delivery orifice 150k. The lower end of the bore 170k is closed by a Welch plug 174k.

The wall, barrier or abutment 299 is provided with an opening or open area 304 for admitting air into the chamber 301 for aerating the fuel in the chamber. The sleeve portion 300 of the member 298 is provided with openings 305, 306 and 307. The opening 307 is preferably opposite or aligned with the fuel delivery orifice 150k, and the openings 305 and 306 preferably disposed upon an axis normal to the axis of the opening 307. The openings 305, 306 and 307 assist in the aspiration of fuel from the main orifice and some fuel from the main orifice is delivered through these openings promoting dispersion or distribution of fuel in the air stream moving through the mixing passage 62k to provide a more homogeneous mixture.

The openings 305 and 306 may be varied in position lengthwise of the control chamber 301 as desired. The openings 305 and 306 are illustrated as being disposed closer to the wall 299 than the opening 307. The openings 304, 305, 306 and 307 additionally provide a venting means or relief area to control the reduction of the mixture rebound velocity and hence the extent of increase in pressure in the chamber 301 upon mixture rebound. The arrangement shown in FIGS. 28 and 29 is particularly usable in carburetors for use with engines wherein closing of the mixture inlet port to the engine causes comparatively high rebound velocities. The openings may be varied in size or position to limit or restrict the mixture rebound velocity and the increase in pressure on rebound in the chamber 301 to attain effective mixture rebound control.

FIGS. 30 and 31 illustrate another form of mixture rebound velocity and pressure control arrangement in the mixing passage adjacent the main fuel delivery orifice. The carburetor body 60m is fashioned with a mixing passage 62m which includes a Venturi 64m and an air inlet region 67m. Disposed in the mixing passage is a means or member 310 which includes a barrier, abutmentor wall 31 1 and a cylindrically-shaped sleeve portion 312, the sleeve portion having a hollow interior providing a control chamber 314.

The surface 315 of the sleeve portion defining the chamber 314 is of partial toroidal curvature and flared outwardly toward' the outlet 316 of the chamber 314 in the direction of normal flow of mixture in the mixing passage. A fitting 172m is threaded into a bore 170m in the body 60m and provides a main fuel delivery orifice 150m. The lower end of the bore 170m is closed by a Welch plug 174m.

In this form of the invention the wall 311 may be imperforate, this form being usable in carburetors with engines wherein the rebound or velocity of reverse flow of the fuel mixture upon closing of the mixture inlet port is not very severe or comparatively low. The sleeve portion 312 is provided with an opening or open area 318 to facilitate engine aspiration of fuel from the main orifice 150m and to control reduction in mixture rebound velocity. Some fuel delivered from the orifice 150m flows through the opening 318 to provide for good distribution of fuel in the main air stream flowing through the mixing passage in addition to the fuel delivered into the air stream from the outlet of the control chamber 314.

The size and relative position of the opening or open area 318 may be varied depending upon the fuel demand required by the engine and the mixture rebound velocities occurring upon closing of the inlet port of a particular engine. In the form shown in FIGS. 30 and 31, the absence of an opening or open area in the wall 311 provides a substantially isolated control chamber 314, except for the vent opening 318, effective to reduce the velocity of the reversely flowing or rebound mixture at the region of the main orifice 150m to restrict or reducedelivery of fuel from 'the main orifice 150m during a rebound mixture flow period following each closing of the mixture inlet port.

The arrangement shown in FIGS. 30 and 31 is desirable where rebound is not severe and that the pressure increase on rebound occurring in the control chamber 314 restricts but does not prevent continued delivery of some fuel through the orifice 150m during rebound so that upon subsequent normal engine aspiration fuel delivery is simply increased. Thus the substantial reduction in delivery of fuel during periods of rebound control does not result in the delivery of an excess amount of fuel which, without the rebound control, would otherwise enrichen the mixture and reduce the power of the engine.

FIGS. 32 and 33 illustrate a form of mixture rebound velocity and pressure control arrangement in association with a small or supplemental Venturi disposed within a main Venturi of a mixing passage. The carburetor body 6011 is fashioned with a mixing passage 62n, the passage including a main Venturi 64n and an air inlet region 67n. Formed integrally in the mixing passage within the main Venturi and at one side region of the mixing passage is a supplemental Venturi 320 having a restricted region 322, an air inlet region 323 and an outlet 324.

The carburetor body 60n is fashioned with a bore 170;: having a threaded portion accommodating a threaded fitting l72n of the character illustrated in FIGS. 9 and 10, the lower end of the bore being closed by a Welch plug 174n. The upper open end of the'fitting l72n provides a fuel delivery orifice l50n. In this form of the invention, a means or member 326 extends into the supplemental Venturi 320 preferably adjacent the choke band or restricted region of the main Venturi 64n. The member 326 has a tubular portion 327, the lower end of which terminates in an outwardly extending flange or ledge 328.

The carburetor body 60n is provided with a bore snugly receiving the tubular portion 327, a counterbore accommodating the flange or ledge 328. The upper end of the fitting 172n engages the ledge 328 to retain the member 326 in the position shown in FIG. 32. The hollow interior or chamber 330 is in alignment with the main fuel delivery orifice 150n. The portion 331 of the member 326 extending into or disposed in the supplemental Venturi 321 is of semiannular cross section providing an opening or outlet 332 downstream of the Venturi 320.

The upper end region of the semiannular portion 331 of member 326 terminates in a semiconically shaped portion 333 providing a cap or cover. Under engine operation fuel from a fuel chamber of the character shown at in FIG. 4 is delivered by aspiration through the main orifice l50n into the chamber 330 and is entrained in the air stream flowing through the supplemental Venturi, and this fuel and air mixture diffused or distributed into the main air stream flowing through the large or main Venturi 6'4n for normal engine operation.

The semiannular wall portion 331 provides a barrier for restricting or impeding reverse flow or rebound of the mixture adjacent the orifice n. The semiconically shaped cap or cover 333 and the semiannular portion 331 define the rebound control chamber 330. The barrier provided by the portions 331 and 333 may be comparatively small when used or associated with a small supplemental Venturi 320 as the air flow through the supplemental Venturi is at high velocity providing ample aspiration for delivering fuel from the orifice 150n through the control chamber 330 into the small Venturi 320 thence into the main Venturi 6411.

Upon reverse flow of mixture or rebound occurring following periods of closing of the mixture inlet port to the engine, the barrier provided by the portions 331 and 333 restricts reverse flow of the mixture at this region, reducing the velocity of the rebound mixture at this region and increasing the pressure in the control chamber 330 to restrict or substantially reduce delivery of fuel from the orifice 150n into the control chamber 330.

The member 331 is proportioned in size so that the increase in pressure developed during rebound in the control chamber 330 is insufficient to prevent discharge of fuel from the orifice 150n but is of such calibration that fuel is continuously delivered from the orifice 150n although in a reduced amount during rebound periods so that the normal mixture of fuel and air will not be rendered too lean in fuel upon normal engine aspiration occurring after each closing period of the fuel inlet port to the engine. I

FIGS. 34, 35 and 36 illustrate a form of mixture rebound velocity and pressure control arrangement in association with a supplemental Venturi, the arrangement being similar to that shown in FIGS. 32 and 33. As shown in FIGS. 34, 35 and 36, the carburetor body 60p is fashioned with a mixing passage 62p, the passage including a main Venturi 64p and an air inlet region 67p. Formed integrally in the mixing passage and at one side region of the mixing passage is a supplemental Venturi 336 having a choke band or restricted region 337, an air inlet region 338 and a mixture outlet region 339.

The body 60p is provided with a bore 170p having a threaded portion accommodating a threaded fitting 172p. of the character illustrated in FIGS. 9 and 10, the lower end of the bore being closed by a Welch plug 174p. The upper open end of the fitting 172p provides a fuel delivery orifice 150p. A tubular means or member 341 projects or extends into the choke band region 337 of the supplemental Venturi 336. The member 341 is of tubular cylindrical shape provided at its lower end with an outwardly extending flange or ledge 342, the body 60p being provided with a bore snugly receiving the tubular member 341, the flange or ledge 342 being accommodated in a counterbore adjacent the upper end of the fitting 172p.

The fitting 172p in assembled position retains the member 341 in the position shown in FIG. 34. The hollow interior of the tubular member 341 provides a rebound control chamber 343 in alignment with the fuel delivery orifice 150p. The upper end of the tubular member 341 is preferably provided with a conically shaped cover or cap portion 344. The region of the wall of the tubular member 341 adjacent the air inlet region of the mixing passage is fashioned with a comparatively small opening or open area 346, and the region of the wall of member 341 downstream of the Venturi 336 is fashioned with an opening or open area 347 as particularly shown in the enlarged view, FIG. 36.

The opening 346 admits air into the control chamber 343 for aerating the fuel in the chamber 343. The opening or open area 347 in the member 341 is of substantial size or area to accommodate entrance of reversely flowing mixture on rebound, the mixture entering the 24 opening 347 impinging against the unperforated region of the member opposite the opening 347 reducing the velocity of the rebound mixture thereby increasing the pressure in the control chamber 343 and reducing or restricting delivery of fuel from the orifice 150p during rebound periods.

The openings or open areas 346 and 347 are calibrated in size suitable to perform effectively under the rebound characteristics of the engine with which the carburetor may be used to reduce the velocity of the rebound mixture at the control chamber to a value at which a small amount of fuel will be aspirated into the control chamber 343 but which is insufficient to enrichen the normal fuel and air mixture moving through the mixing passage and through the small Venturi 336. The delivery of a small amount of fuel during rebound periods establishes a continuity of fuel delivery into the control chamber so that there is no delay in the aspiration of fuel under normal air flow conditions following periods of mixture rebound.

FIGS. 37 through 39 illustrate another form of the invention for use in a mixing passage of a carburetor without a supplemental Venturi. The carburetor body r is fashioned with a mixing passage 62r, the passage including a Venturi 64r and an air inlet region 67r. The body 60r is provided with a bore 170r having a threaded portion accommodating a threaded fitting l72r of the character illustrated in FIGS. 9 and 10. The upper open end of the fitting 172r provides a fuel delivery orifice l50r.

A tubular means or member 350 projects or extends into the choke band region r of the Venturi 64r. Member 350 is of tubular cylindrical shape provided at its lower end with an outwardly extending flange or ledge 351. The body 60r is provided with a bore snugly receiving the tubular member 350, the flange or ledge 351 being accommodated in a counterbore in the body adjacent the upper end of the fitting 172r, the fitting l72r retaining the member 350 in the position shown in FIGS. 37 and 39.

The hollow interior of the tubular member 350 provides a rebound control chamber 352 in communication with the fuel delivery orifice l50r. The upper end of the tubular member 350 is fashioned with a cover or cap portion 353 generally conical in shape. The region of the wall of the tubular member 350 adjacent the air inlet region of the mixing passage is provided with a comparatively small opening or open area 354, and the region of the wall of member 350 downstream of the mixing passage is provided with an opening or open area 355 shown in FIGS. 37 and 39.

The comparatively small opening 354 admits air into the control chamber 352 for aerating the fuel in the chamber. The opening or open area 355 is of substantial size or area in order to accommodate delivery of fuel and air from the chamber 352 into the main air stream and the entrance of reversely flowing mixture on mixture rebound. The wall region defining the opening 355 is preferably of conical shape to enhance the entrance of rebound mixture into the control chamber.

The rebound mixture adjacent the opening 355 enters the opening and is impinged against the unperforated wall region of member 350 adjacent the opening 354 to substantially reduce the velocity of the rebound mixture and thereby increase the pressure in the control chamber 352, restricting or reducing delivery of fuel from the fuel delivery orifice r during rebound 

1. A system for substantially preventing delivery of an overrich fuel and air mixture to an internal combustion engine during engine operation including delivering fuel from an orifice under the influence of engine aspiration into an air stream flowing through an induction passage providing a combustible fuel and air mixture at the region of a mixture inlet port of the engine, interrupting normal mixture flow by the closing of the inlet port to the engine thereby effecting a reversal in direction of mixture flow in the induction passage, and reducing the velocity of the reversely flowing mixture at the region of delivery of fuel into the passage during periods of closing of the inlet port to reduce delivery of fuel into the passage at such periods.
 2. A system for substantially preventing delivery of an overrich fuel and air mixture to an internal combustion engine during engine operation including delivering fuel from an orifice under the influence of engine aspiration into an air stream flowing through an induction passage providing a combustible fuel and air mixture at the region of a mixture inlet port of the engine, interrupting normal mixture flow by the closing of the inlet port to the engine thereby effecting a reversal in direction of mixture flow in the induction passage, and impeding the flow of the reversely flowing mixture at the region of delivery of fuel into the passage during periods of closing of the inlet port to retard delivery of fuel into the passage at such periods.
 3. The method of controlling the ratio of fuel to air in a combustible mixture supplied through a mixing passage to the engine through an inlet port wherein fuel is aspirated from an orifice into the air stream by the velocity of the air stream, abruptly impeding flow of the mixture by the closing of the inlet port whereby the mixture is caused to flow in a reverse direction through the mixing passage, and reducing flow of the combustible mixture in the reverse direction adjacent the region of delivery of fuel into the mixing passage to reduce apsiration of fuel from the orifice during periods of reverse flow of mixture in the mixing passage.
 4. A method of substantially preventing delivery of an overrich fuel and air mixture to an internal combustion engine during engine operation including delivering fuel from an orifice under the influence of engine aspiration into an air stream flowing through an induction passage providing a combustible fuel and air mixture at the region of a mixture inlet port of the engine, impeding normal mixture flow by the closing of the inlet port to the engine thereby effecting a reversal in direction of mixture flow in the induction passage, and increasing the pressure at the region of fuel delivery into the passage during periods of closing of the inlet port to reduce delivery of fuel into the passage at such periods.
 5. The method according to claim 4 including varying the amplitude of increase in pressure to regulate the delivery of fuel at such periods.
 6. A method of substantially preventing delivery of an overrich fuel and air mixture to an internal combustion engine during engine operation including delivering fuel from an orifice under the influence of engine aspiration into an air stream flowing through a fuel and air mixing passage providing a combustible fuel and air mixture at the region of a mixture inlet port of the engine, impeding normal mixture flow upon closing of the inlet port effecting a reversal in direction of mixture flow in the mixing passage, isolating a portion of the reversely flowing mixture at a control chamber adjacent the delivery of fuel into the passage, and reducing the velocity of the reversely flowing mixture isolated at the chamber to reduce delivery of fuel into the passage during periods of closing of the inlet port.
 7. The method according to claim 6 including venting the control chamber to regulate delivery of fuel into the passage during periods of closing of the inlet port of the engine.
 8. A system for substantially preventing delivery of an overrich fuel and air mixture to a two cycle engine of the three port type wherein the piston of the engine controls delivery of combustible fuel and air mixture from an inlet port into the engine crankcase including delivering fuel from a fuel chamber by engine aspiration into a passage in communication with the inlet port and wherein during closed periods of the inlet port the mixture in the passage is caused to flow in a reverse direction in the passage, retarding the velocity of a portion of the reversely flowing mixture by a control chamber in the passage, and reducing delivery of fuel into the passage at the region of the control chamber during periods of closing of the mixture inlet port by the piston of the engine.
 9. A system according to claim 8 including venting the control chamber to regulate the reduction in velocity of the reversely flowing mixture at the control chamber.
 10. A system for substantially preventing delivery of an overrich fuel and air mixture to a two cycle engine of the three port type wherein the piston of the engine controls delivery of combustible fuel and air mixture from an inlet port into the engine crankcase including delivering fuel from a fuel chamber by engine aspiration into a passage in communication with the inlet port and during closed periods of the inlet port the mixture is caused to flow in a reverse direction in the passage, restricting flow of a portion of the reversely flowing mixture by a barrier adjacent the region of delivery of fuel into the passage to reduce delivery of fuel into the passage during the periods that the inlet port is closed, and venting the barrier to control the extent of reduction in delivery of fuel into the passage during periods of closing of the mixture inlet port by the piston of the engine.
 11. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, an orifice opening into the mixing passage for delivering fuel under the influence of engine aspiration from the fuel chamber into the mixing passage, a throttle valve for controlling flow of fuel and air mixture to the engine having a mixture inlet port which is intermittently closed and opened during engine operation, and means at the region of delivery of fuel into the mixing passage effective during the periods of closing of the mixture inlet port to reduce delivery of fuel into the mixing passage.
 12. Charge forming apparatus including, in combination, a body construction provided with an air and fuel mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, an orifice opening into the mixing passage for delivering fuel under the influence of engine aspiration from the fuel chamber into the mixing passage, a throttle valve for controlling flow of fuel and air mixture to an internal combustion engine having a mixture inlet port which is intermittently closed during engine operation, and means disposed in the mixing passage for reducing the velocity of a portion of the mixture flowing in a revErse direction during the periods of closing of the mixture inlet port to reduce aspiration of fuel into the mixing passage during the periods that the mixture inlet port is closed.
 13. The combination according to claim 12 wherein the means in the mixing passage includes a barrier at the upstream side of the region of delivery of fuel into the mixing passage.
 14. The combination according to claim 13 wherein the barrier has an open area for regulating the extent of reduction of the velocity of the mixture flowing in a reverse direction at the region of delivery of fuel into the mixing passage.
 15. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, a fuel delivery orifice for delivering fuel from the fuel chamber by engine aspiration, a throttle valve for controlling flow of fuel and air mixture to an engine having a mixture inlet port which is intermittently closed during engine operation, means providing a control chamber in the mixing passage into which the fuel is delivered from the orifice, said control chamber having an open area downstream of the mixing passage whereby fuel delivered into the chamber is delivered into the air stream flowing through the mixing passage, said chamber being effective to reduce the velocity of the mixture flowing in a reverse direction at the control chamber during periods of closing of the mixture inlet port to reduce delivery of fuel into the mixing passage during said periods.
 16. The combination according to claim 15 wherein the chamber has a vent opening for controlling the reduction in velocity of the reversely flowing mixture at the chamber to regulate the delivery of fuel into the chamber during the periods that the mixture inlet port is closed.
 17. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, a fuel orifice for delivering fuel under the influence of engine aspiration, a throttle valve for controlling flow of fuel and air mixture to an engine having a mixture inlet port which is intermittently closed during engine operation, means providing a walled chamber in the mixing passage adjacent the fuel delivery orifice and into which fuel is delivered for distribution into the air stream moving through the mixing passage, said walled chamber having a wall region at the upstream side of the fuel delivery orifice and an outlet downstream of the mixing passage, a lengthwise wall region of the chamber being flared in the downstream direction toward its outlet region, said walled chamber being of a configuration to reduce the velocity of a portion of the mixture flowing in a reverse direction during the periods of closing of the mixture inlet port and reduce delivery of fuel into the mixing passage during the periods that the mixture inlet port is closed.
 18. The combination according to claim 17 wherein the wall of the walled chamber at the upstream side of the fuel delivery orifice has an open area to admit air into the chamber for aerating the fuel delivered into the walled chamber, said open area being of substantially less cross sectional area than the transverse cross sectional area of the control chamber.
 19. The combination according to claim 18 wherein the open area in the wall is at a region spaced from the fuel delivery orifice.
 20. The combination according to claim 18 wherein the open area in the wall of the chamber comprises a plurality of spaced openings, the combined cross sectional area of the openings being substantially less than the transverse cross sectional area of the control chamber.
 21. Charge forming appaRatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, and means disposed in the mixing passage at the region of delivery of fuel from the orifice having a hollow interior for receiving fuel delivered from the orifice, said means having a wall region at the upstream side of the fuel delivery orifice, said means having an outlet downstream of the mixing passage through which fuel from the interior of the means is aspirated into the air stream moving through the mixing passage.
 22. The combination according to claim 21 wherein the wall region of the means at the upstream side of the fuel delivery orifice is provided with an open area for admitting air into the interior of the means for aerating the fuel therein, said open area being of less cross sectional area than the cross sectional area of the outlet opening.
 23. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, the mixing passage including a Venturi configuration, and means disposed in the mixing passage at the region of delivery of fuel from the orifice providing a chamber having its longitudinal axis substantially parallel with the axis of the mixing passage, said chamber adapted to receive fuel from the fuel delivery orifice, said means having a wall region adjacent to and at the upstream side of the fuel delivery orifice, said chamber having an outlet downstream of the mixing passage adjacent the Venturi through which fuel from the interior of the chamber is aspirated into the air stream moving through the mixing passage.
 24. The combination according to claim 23 wherein the wall region is provided with an open area for admitting air into the chamber for aerating the fuel therein, said open area being of less cross sectional area than the transverse cross sectional area of the chamber.
 25. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, the mixing passage including a main Venturi, a supplemental Venturi in the main Venturi, a tubular member disposed in the supplemental Venturi at the region of delivery of fuel from the orifice arranged to receive fuel aspirated from the orifice, the axis of the tubular member being normal to the axis of the supplemental Venturi, the wall of the tubular member downstream of the mixing passage having an open area providing an outlet through which fuel from the interior of the member is aspirated into the air stream moving through the mixing passage.
 26. Charge forming apparatus including, in combination, a carburetor having a body provided with a fuel and air mixing passage, a fuel chamber in the carburetor body, a flexible diaphragm forming a wall of the fuel chamber, a fuel inlet valve in the body, means transmitting movement of the diaphragm to thE inlet valve to control fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, means disposed in the mixing passage integral with the body providing an elongated chamber adjacent the fuel delivery orifice and into which fuel is delivered from the orifice for distribution into the air stream moving through the mixing passage, said means having a wall at the upstream side of the fuel delivery orifice extending substantially transversely of the axis of the mixing passage, said chamber having an outlet downstream of the mixing passage, said transversely disposed wall having an open area admitting air to the chamber for aerating the fuel in the chamber, said open area in the transversely disposed wall being of less cross sectional area than the cross sectional area of the chamber.
 27. Charge forming apparatus including, in combination, a carburetor having a body provided with a fuel and air mixing passage, a fuel chamber in the carburetor body, a flexible diaphragm forming a wall of the fuel chamber, a fuel inlet valve in the body, means transmitting movement of the diaphragm to the inlet valve to control fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, means disposed in the mixing passage providing a walled chamber adjacent the fuel delivery orifice and into which fuel is delivered for distribution into the air stream flowing through the mixing passage, said chamber being elongated lengthwise of the mixing passage and having a wall at the upstream side of the fuel delivery orifice disposed substantially transversely of the axis of the mixing passage, said chamber having an outlet downstream of the mixing passage, a lengthwise wall region defining at least a portion of the chamber being flared outwardly in a downstream direction toward the outlet of the chamber.
 28. The combination according to claim 27 wherein the means providing the walled chamber is integral with the body.
 29. The combination according to claim 28 wherein the transversely extending wall of the walled chamber has an opening for admitting air into the chamber for aerating the fuel in the chamber.
 30. The combination according to claim 28 wherein the lengthwise wall region of the chamber has an open area for venting the chamber.
 31. Charge forming apparatus including, in combination, a carburetor having a body provided with a fuel and air mixing passage, a fuel chamber in the carburetor body, a diaphragm forming a wall of the fuel chamber, a fuel inlet valve in the body, means transmitting movement of the diaphragm to the inlet valve to control fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, means disposed in the mixing passage providing an elongated chamber adjacent the fuel delivery orifice and into which fuel is delivered from the orifice for distribution into the air stream moving through the mixing passage, said means having a wall at the upstream side of the fuel delivery orifice extending substantially transversely of the axis of the mixing passage, said chamber having an outlet downstream of the mixing passage, a lengthwise wall region of the chamber being flared outwardly in a downstream direction toward its outlet, said transversely disposed wall having an open area admitting air to the chamber for aerating the fuel in the chamber, said open area in the transversely disposed wall being of less cross sectional area than the transverse cross sectional area of the chamber.
 32. Charge forming apparatus including, in combination, a carburetor having a body provided with a fuel and air mixing passage, a fuel chamber in the carburetor body, a flexible diaphragm forming a wall of the fuel chamber, a fuel inlet valve in the body, means transmitting movement of the diaphragm to the inlet valve to control fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, a member of generally tubular configuration extending into the mixing passage and disposed to receive fuel delivered from the orifice, said member having a cap portion at its end region, the wall region of the tubular member downstream of the mixing passage having an open area providing an outlet for the delivery of fuel from the interior of the tubular member into the mixing passage.
 33. The combination according to claim 32 wherein the wall region of the member upstream of the mixing passage has an opening for admitting air from aerating fuel in the member.
 34. Charge forming apparatus including, in combination, a carburetor having a body provided with a fuel and air mixing passage, said mixing passage including a main Venturi, a fuel chamber in the carburetor body, a diaphragm forming a wall of the fuel chamber, a fuel inlet valve in the body, means transmitting movement of the diaphragm to the inlet valve to control fuel flow from a supply into the fuel chamber, a fuel delivery orifice in communication with the fuel chamber for delivering fuel under the influence of engine aspiration, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, a supplemental Venturi in the mixing passage adjacent the fuel delivery orifice, a member of generally tubular configuration extending into the supplemental Venturi and disposed to receive fuel delivered from the orifice, the wall region of the tubular member downstream of the mixing passage having an open area providing an outlet for the delivery of fuel from the interior of the tubular member into the mixing passage.
 35. The combination according to claim 34 wherein said tubular member has a cap portion at its end region.
 36. The combination according to claim 34 wherein the wall region of the tubular member upstream of the mixing passage has an opening for admitting air for aerating the fuel in the tubular member.
 37. The combination according to claim 35 including a vent opening in the cap portion of the tubular member.
 38. Charge forming apparatus including, in combination, a body construction provided with a mixing passage and a fuel chamber, a fuel inlet for the body construction, valve means for the fuel inlet, control means for said valve means for regulating fuel flow from a supply into the fuel chamber, an orifice opening into the mixing passage for delivering fuel under the influence of engine aspiration from the fuel chamber into the mixing passage, a throttle valve in the mixing passage for controlling flow of fuel and air mixture, the mixing passage including a Venturi configuration, tubular means disposed in the body at the region of the Venturi, said tubular means providing a chamber in which fuel is delivered from the fuel delivery orifice, the chamber having an outlet downstream of the mixing passage for delivery of fuel from the chamber provided by the tubular member into the mixing passage, said tubular means having a transverse wall upstream of the mixing passage, and a plurality of sapced openings in the transverse wall for admitting air into the chamber for aerating fuel therein. 